Add frontend for block all requests in admin/network settings

What does this MR do and why?

Add checkbox and warning alert to block all requests in admin/network settings.

This feature is behind the feature flag deny_all_requests. There are pending backend changes in !110599 (merged) that are WIP (and maybe more MRs) before we roll out this feature.

Screenshots or screen recordings

Description	Before	After (without feature flag)	After (with feature flag)
Outbound requests - Allow selected
Outbound requests - Block selected (if available)

How to set up and validate locally

1. Go to Admin > Settings > Network and expand the Outbound requests section. For example, http://127.0.0.1:3000/admin/application_settings/network#js-outbound-settings.
2. Enable the feature flag deny_all_requests in a rails console.
3. Apply the below diff to preview the changes.

diff --git a/app/views/admin/application_settings/_outbound.html.haml b/app/views/admin/application_settings/_outbound.html.haml
index ec2f064d085b..aa2dab1f2c00 100644
--- a/app/views/admin/application_settings/_outbound.html.haml
+++ b/app/views/admin/application_settings/_outbound.html.haml
@@ -1,4 +1,4 @@
-- deny_all_requests = Feature.enabled?(:deny_all_requests) ? @application_setting.deny_all_requests : false
+- deny_all_requests = Feature.enabled?(:deny_all_requests) ? @application_setting.dns_rebinding_protection_enabled : false
 
 = gitlab_ui_form_for @application_setting, url: network_admin_application_settings_path(anchor: 'js-outbound-settings'), html: { class: 'fieldset-form' } do |f|
   = form_errors(@application_setting)
@@ -6,7 +6,7 @@
   %fieldset
     .form-group
       - if Feature.enabled?(:deny_all_requests)
-        = f.gitlab_ui_checkbox_component :deny_all_requests,
+        = f.gitlab_ui_checkbox_component :dns_rebinding_protection_enabled,
             s_('OutboundRequests|Block all requests, except for IP addresses, IP ranges, and domain names defined in the allowlist'),
             checkbox_options: { class: 'js-deny-all-requests' }
         = render Pajamas::AlertComponent.new(variant: :warning,

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #377371 (closed)